Various types of hydraulic tools such as wrenches or pliers which may be held in one hand are known. The vast majority of these, however, require both hands of an operator to effect tool engagement or disengagement with the workpiece.
U.S. Pat. No. 3,058,214 of the present inventor shows a one-hand hydraulic tool comprising a frame and a stationary jaw fixed thereto; a movable jaw pivotally mounted in the frame for movement towards and away from the stationary jaw and including a cam member; a hydraulic power system disposed in the frame and including a liquid tank, a piston reciprocable in a cylinder and adapted to be pressed unconnectedly against the cam member of the movable jaw, thereby to impart a moment to the movable jaw, a pump connected to the tank by a suction duct and to the cylinder by a delivery duct, check valves in the suction and delivery ducts, a return duct from the cylinder to the tank, and a pressure release valve in the frame member for the operation of the tool; springy means acting on the movable jaw in opposition to the moment imparted to the movable jaw by the pressure exerted on the cam member by the hydraulic piston; and non-hydraulic means for mechanically imparting to the movable jaw a moment co-directional with the moment imparted to the movable jaw by the piston.